This application claims the priority of German patent document 100 46 221.9, filed Sep. 19, 2000, the disclosure of which is expressly incorporated by reference herein.
This invention relates to a process and a device for the control of selective cylinder filling in combustion engines with variable valve operation where the valve closing and opening times of the cylinder intake valves are controllable.
Variable valve drives in combustion motors are generally known. An eccentric shaft is mostly adjusted to control the stroke height of the intake valves. To adjust the eccentric shaft, an electric motor is often used; but a hydraulic system or other systems for adjusting the eccentric shaft or similar valve drive adjusting systems can also be used.
Depending on the system for a valve drive, there are production tolerances, for example, in the case of the valve head, in a roll drag lever, in an intermediate lever or in the eccentric shaft itself. These production tolerances lead to differences in filling the individual cylinders. This results in a xe2x80x9crough runningxe2x80x9d of the motor, especially during idle running. In the case of direct-injection engines, this can lead to the run limit being reached, at which there is no further combustion in the cylinder.
A perceptible rough running in a vehicle, however, as a rule, is not tolerable. Therefore, attempts have been made to achieve uniform filling distribution within a range of +/xe2x88x9210 percent by compressing the production tolerances. That range mostly represents an acceptable filling difference. Minimizing the production tolerances, however, is very expensive. By way of example, the individual components must be measured. In the extreme case, it may even be necessary to dismantle a cylinder head with the subsequent follow-up work.
The object of the invention is, in combustion engines with variable valve operation, to achieve satisfactory idling comfort or adequate quiet running at low rpms even with standard production tolerances.
This problem is solved by the process and apparatus for controlling cylinder selective filling in a combustion engine with a variable valve drive, where the valve stroke and/or the valve closing and opening times of the cylinder intake valves are controllable. At least one input magnitude is determined. Based on the input magnitude a conclusion is drawn as to the filling or filling differences of the cylinder. From this input magnitude, a control signal is determined for the variable drive in such a way that any different fillings of the cylinder are balanced out by adjusting the valve drive.
A basic feature behind certain preferred embodiments of the invention involves the use of the variable valve drive to balance out any differences in the cylinder filling. To recognize any differing cylinder filling, either rough running magnitudes (for example, number of revolutions, torque), valve stroke magnitudes (for example, direct-valve stroke) or other magnitudes that point to differing filling conditions (for example, lambda signal) are used. On the basis of these input magnitudes, a control magnitude is generated in a control device. By using the control magnitude, an actuator of the valve drive is impacted so that during the time between fillings of the cylinders to be filled in succession, a different adjustment can be brought about on the valve drive, for example, in the eccentric shaft. By selective cylinder adjustment of the eccentric shaft, especially in the idling range, the valve lifting curves can be changed so that a filling difference caused in itself by production tolerances can be balanced out.
When several intake valves per cylinder are used, then one can also average via these valves. This is particularly advantageous when the valve stroke or the opening time of a valve is used as the input magnitude.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.